Change the overlaying order of lines in ggplot

Question

Suppose I have this plot:

library(ggplot2)
pl_data <- data.frame(x = rep(c(1, 2), times = 3), y = c(0, 1, 1, 0, .7, .7), col = rep(c("r", "b", "g"), each = 2))
ggplot(pl_data, aes(x = x, y = y, color = col)) +
  geom_line(size = 3)

How can I change the plotting order, so that the red line is plotted above the other two?

The background therefore is that I have plots with very similar lines, and want to see specific lines in the foreground.

I suppose something along the lines of this answer order of stacked bars in ggplot would work. It makes the color column to factors and changes their order, but I would prefer to change this directly in a line of the ggplot call.

I also tried changing the legend order with scale_color_discrete(breaks=c("r", "g", "b"))), but that does not effect the plotting order either.

Answer 1

library(ggplot2)
df <- data.frame(
  x = rep(c(1, 2), times = 3), 
  y = c(0, 1, 1, 0, .7, .7), 
  col = rep(c("r", "b", "g"), each = 2))

ggplot() + 
  geom_line(data = df[3:4,], aes(x = x, y = y), color = 'blue', size = 3) +
  geom_line(data = df[5:6,], aes(x = x, y = y), color = 'green', size = 3) +
  geom_line(data = df[1:2,], aes(x = x, y = y), color = 'red', size = 3)

Answer 2

hi when you are plotting lines it is the group ID - the highest group ID goes on top